The main emphasis of the proposed research project will be directed toward the study of the mechanisms responsible for the maintenance of chronicity in inflammatory processes produced by local deposition of antigen. The experimental model to be used is the chronic synovitis produced by intra-articular injection of soluble antigen in rabbits previously immunized to the antigen. It has been shown in detailed studies of this experimental chronic arthritis carried out in this laboratory that the local antigen is retained for long periods of time in the form of immune complexes not in synovium but in acellular collagenous joint tissue. It is proposed to investigate (a) the mechanism whereby these immune complexes may sustain a prolonged chronic inflammatory process; (b) the mode of association of the immune complexes to collagenous tissue and its components, i.e. collagen and interfibrillar matrix; (c) the possible binding of immunoglobulin to one of the components of collagenous tissue as a basis for the persistence of the immune complexes retained in this tissue and (d) the presence and nature of immunoglobulin associated with collagenous tissues obtained from patients with rheumatoid arthritis, osteoarthritis or traumatic arthritis. BIBLIOGRAPHIC REFERENCES: Jasin, H.E., The mechanism of trapping of immune complexes in experimental antigen-induced arthritis. In Immunological Aspects of Rheumatoid Arthritis, S. Karger, Basel, Rheumatology 6:288-292, 1975. Cooke, T.D.V., Richer, S., Hurd, E., and Jasin, H.E., Localization of antigen-antibody complexes in intraarticular collagenous tissues, Ann. N.Y. Acad. Sci. 256:10-24, 1975.